Pipe clamp assemblies and bar clamp assemblies, hereinafter collectively referred to as beam clamp assemblies, are commonly used to hold workpieces or other articles in a fixed position for various operations such as cutting, drilling, nailing, screwing, gluing, etc. Beam clamp assemblies generally comprise a linear beam (e.g., a pipe, rod or bar), and a pair of opposing jaws, at least one of which is slidably supported on the beam. A first of the jaws is either fixed to one end of the beam or includes a locking device for holding the jaw in a selected position on the beam. A linear actuator is provided to linearly advance the second jaw toward and away from the first jaw to apply and relieve pressure on an article interposed between the jaws. Typically, the jaws of beam clamp assemblies have parallel opposing gripping surfaces. Accordingly, beam clamp assemblies are generally adapted for clamping workpieces or other articles having flat, parallel opposing surfaces. However, in order to clamp a variety of articles or workpieces at nonplanar surfaces or surfaces which are not parallel to the gripping surface of the jaws, specially designed fixtures or jigs are generally utilized. For example, to grip the corner of a picture frame, specially configured miter jigs having mitered gripping surfaces have been designed. These specialty jigs have been provided with integral fasteners, such as sockets or clips, to allow attachment of the jigs to the jaws of the beam clamp assembly. A disadvantage with conventional jigs is that they are designed for attachment to a particular type or model of beam clamp assembly and cannot be used interchangeably with beam clamp assemblies having jaw gripping surfaces of a size or shape which is not suitably configured to cooperatively receive the integral fasteners on the jigs. This lack of interchangability can be a disadvantage and inconvenience to workers who must match the jig for a particular job to a specific type of beam clamp assembly which may, for example, be unavailable because it is being used for another job.
It is desirable that jigs or fixtures used for clamping a particular type of workpiece or article be firmly secured to the jaws of the beam clamp assembly to prevent shifting of the fixtures relative to the workpiece or article during clamping and subsequent operations. As a result, the dimensional tolerances between the jaws and the integral fasteners on the jigs are extremely low. Consequently, another disadvantage with conventional clamping fixtures is that installation of the fixtures onto the jaws and removal of the fixtures from the jaws can be relatively difficult and time consuming.
When a beam clamp assembly is used without a special fixture or jig, such as to clamp an article or workpiece having opposing parallel, planar surfaces, it is generally desirable to provide a protective layer between the gripping surfaces of the jaws and the gripped surfaces of the article or workpiece being clamped, to prevent abrasion of the surface of the clamped article or workpiece by irregularities, such as bumps and protuberances, which are generally inherently formed during casting of steel jaws. For this purpose, rubber clamp pads which can be slipped over the gripping surfaces of the jaws have been provided. While conventional clamping pads provide some protection against abrasion, there are several disadvantages associated with their use. Included among the disadvantages of conventional rubber, slip-on clamping pads is that because of the flexibility and deformability of the rubber pads, true clamping pressure between the jaws and the workpiece is not achieved, and the rubber pads can tend to slip or shift relative to the jaws during clamping or subsequent operations on a workpiece being clamped. Another disadvantage with conventional beam clamping systems and rubber clamping pads is that the rubber clamping pads must be removed when a specialty clamping fixture is used, and replaced when it is desired to again use the beam clamp assembly to clamp a workpiece having parallel, planar opposing surfaces. Thus, reconfiguring a beam clamp assembly between a configuration in which a specialty jig is used and one in which clamping pads are used can be difficult and time consuming.